1. Field of the Invention
This invention relates to optical disc drives, and more particularly to a system and a method for adjusting a tilt angle of a light beam related to an optical disc.
2. Description of Related Art
Nowadays, optical discs are widely used for storing information. Related optical disc drives for reproducing/recording data from/onto the optical discs are also widely used.
Referring to FIG. 5, a traditional optical disc drive 500 capable of reproducing/recording an optical disc 600 is illustrated. The optical disc drive 500 includes a spindle motor 502, an optical pickup unit 504, a sled shaft 506, a sled motor 508, and a controller 510. The optical disc 600 is arranged on and rotated at a predetermined velocity by the spindle motor 502. The optical pickup unit 504 is disposed to face a read-out surface of the optical disc 600. The optical pickup unit 504 is movable along a radial direction of the optical disc 600 by the sled motor 508 and the sled shaft 506.
Generally, a light beam emitted by the optical pickup unit 504 is required to be correctly focused onto tracks of the optical disc 600. The tracks are arranged in concentric or spiral manner from an inner side to an outer side of the optical disc 600. During a reproducing or recording process, the optical pickup unit 504 is moved from the inner side to the outer side by the sled motor 508 and the sled shaft 506. However, mechanical parts usually lead to assembling errors, such as the sled shaft 506 assembled in the optical disc drive 500 is usually not absolutely parallel to the optical disc 600. This will cause an oblique angle between a moving path of the optical pickup unit 504 and the optical disc 600. Therefore, a tilt angle of the light beam is required to be adjusted to compensate the oblique angle. A plurality of test parameters are assigned to adjust the tilt angle of the light beam. Generally, the test parameters are derived by testing the disk drive with an ideal glass plate. The test parameters are stored in storage units of the optical disc drive 500, for example, a read only memory (ROM). When the optical disc 600 is loaded in the optical disc drive 500, the test parameters are used to adjust the tilt angle of the light beam so as to correctly focus the light beam onto the tracks.
However, there are many types of optical discs in the market, while a plenty of which are not standard as the ideal glass plate, such as planeness of the optical discs. Especially, recording layers of the optical discs may be warped due to poor quality or improper storage of the optical discs. In this situation, if the light beam is maintained at a same tilt angle during a recording or a reproducing process, the optical discs may be recorded or reproduced incorrectly.
Therefore, an optical disc drive with adjustable tilt angle of the light beam according to the optical discs is desired.